The x-ray visualization of bile ducts and of the gall bladder requires contrast media which are excreted through the liver and gall bladder. All cholegraphics of clinical usefulness and which are to be administered intravenously are of the basis structure IV which was obtained for the first time in iodipamide (formula IVa). See German Pat. Nos. 936,928; 926,545; where for iodipamide IVa, X=--(CH.sub.2).sub.4 --. ##STR2##
Their structural features are the following: 2 tri-iodinated anilines each with one free carboxyl group, with one hydrogen in the 5-position, and a dicarboxylic acid binding the two aromatic nuclei. To date, in conventional commercial cholegraphics, as regards variations in these structural features, the bridge member X has been varied on the one hand, and on the other hand, the hydrogen has been substituted in the 5- and 5'-positions.
Corresponding research using these and similar compounds (see also ROENTGENKONTRASTMITTEL by R. Barke, Georg Thieme publishers, Leipzig 1970, pp. 102--) has led to the observation that each of the structural elements assumes its own significance in the excretion through the gall bladder. In particular, the unsubstituted hydrogen atoms in the 5,5'-positions appear to be necessary for bonding to plasma albumins and transport proteins. Experience has shown that contrast media of formula IV which are substituted in the 5,5'-position by acylamino groups or aminocarbonyl groups may be somewhat more compatible, but much less of them passes through the bile duct; they are more markedly excreted through the kidney (see German Offenlegungsschriften Nos. 1 618 001 and 2 422 718).